UNIX V6 Shell

The original Shell from Version 6 UNIX.

Also contains pwb.c, the PWB/UNIX shell (Bell Labs, 2.44, 5/26/77), ported to modern Unix/Linux.

Notes

Compiled with -ansi, -pedantic and -Wall flags.

Building

cc -ansi -pedantic -Wall -o pwb pwb.c      # PWB shell
cc -ansi -pedantic -Wall -o osh osh.c      # V6 shell

Both also build warning-free under -Wall -Wextra -O2 (except one intentional warning in pwb.c where a global points into main1's stack frame, as in the original design).

PWB shell port notes

pwb.c was ported from V6-era K&R C to ISO C while keeping the original structure and behavior:

• Numeric word-offset macros (#define DCOM 5, t[DCOM]) replaced with real struct member access (t->DARR[i], t->DLEF, ...); word-offset punning is not portable to 64-bit layouts.
• struct tree fields hold either tree links or strings exactly as before; explicit casts mark the punning sites.
• texec() now takes char **argv instead of relying on struct adjacency to synthesize an argv for the ENOEXEC fallback.
• V6 syscalls updated: seek/tell -> lseek, integer signal() values -> SIG_IGN/SIG_DFL, wait status decoded with WIFEXITED/WTERMSIG/WCOREDUMP, times(2) mapped through struct tms.
• K&R implicit int declarations, missing returns, and deprecated register usage cleaned up; builds clean with -ansi -pedantic -Wall.
• The site-specific accounting file (/etc/sha) and .path file are used if present, else sensible defaults (same as the original).